Oil burner switch control



Aug. 13, 1940.

D. C. WI LKERSON OIL BURNER SWITCH CONTROL Filed June 8, 1936 2 Sheets-Sheet 1 2027/1 26, M7e25072 W 9P% Aug. 13, 1940.

@D. c. WILKERSON OIL BURNER SWITCH CONTROL Filed June 8, 1936 2 Sheets-Sheet 2 Patented Aug. 13, 1940 UNITED STATES PATENT OFFICE OIL BURNER SWITQH CONTROL Application .lune 8, 1936, Serial No. 84,13?

12 Claims.

The present invention relates to thermal change responsive mechanism for controlling fuel consuming devices such as oil burners, coal burners, gas burners and the like, wherein safety cut-oif or control means are required to halt or to regulate over a prescribed thermal range, the development of combustion and combustible flow.

The object of the invention is to provide such safety controls adapted to connect and interrupt the action of elements arranged to initiate or close a combustion cycle, upon predetermined temperature variations over a given scale, and to establish such connection and interruption immediately upon increased or reduced temperature at the point of measure.

A specific object of the invention is the pro- Vision of electrically operated combustion control mechanism adapted to cooperate with the safety controls whereby initial movement of the thermal change responsive mechanism on either increasing or decreasing temperature immediately translates such motion into corrective control of the development of combustion, while permitting free overtravel after such corrective control has been established.

A further. object of the invention is the provision of positively acting translating mechanism wherein the release of free movement is definitely gauged by positive mechanical elements as distinct from mechanisms in which friction slip of indeterminate character is utilized. The advantages of positional positive action in the mechanism of the invention will be brought out in the specification which follows.

In competitive devices, wherein purely friction means are utilized to pick up the switch mechanism, an intedeterminate slip takes place upon initial movement of the thermal element, which slip varies according to temperature, atmospheric condensation, spring loading, and the surface coefiicie'nts of friction discs. Wherein absolute and rapid response is required from the switch control mechanism for a high and invariable safety factor, my invention provides a positive initial movement of the switch mechanism in response to the first increment of motion of the thermal element, distinct from such friction mechanisms. Further, at the reversal of the thermal phase in alternation between increasing and decreasing heat, my invention provides the same operation, when the requirements to meet the change of combustion condition are highly critical. In comparison, the structure of my invention yields a relatively instantaneous re-- sponse, thus heightening the safety factor.

(Cl. Nil-J38) Figures Figure 1 is a side elevation of my thermal control device.

Figure 2 is a section taken at line 2-2 of Figure 1.

Figure 3 is a view similar to Figure 2, but showing portions of support means broken away.

Figure 3a is a view of an alternative construc tion to the shaft and key mounting of Figure 2.

Figure 4 is a side elevation in part section, of a modified construction to that of Figure 1, and Figure 5 is a section taken at 5-ti of Figure 4.

Figure 6 represents a second modification of the construction of Figure 1 in side elevation, and Figure 7 is a section taken at l-l of Figure 6, while Figure 8 is a section taken at 53-8 of Figure 6.

Figure 9 shows a detail of section construction taken on 9-9 of Figure 6 in the assembly of Figure 6. Figure 10 is a detail of construction of the blade-and-ball ratchet device shown in Figure 7.

In Figure 1, the numeral l identifies a thermalresponsive element, such as the well-known stack switch of the coal, gas or oil burner of general use. The mounting frame or shell 2 is apertured at 3 to receive control rod or shaft t attached to the movable end of element l at 5. The fixed end of element l is attached to sleeve 6 at i, said sleeve being part of, or adjustably fixed to frame 2, according to the desired mounting construction of the control unit. The element l protrudes in use into any desired combustion space.

At the inner end of rod i is amxed star wheel 9 by key it, threads M, nut l2 and washer it, so that with thermal changes in element 5, wheel 9 acting as a lever rotates positively, clockwise or counterclockwise, as in Figures 2 and 3. Insulator I 4 mounted on shell 2 serves as a heat battle as well as a support for electrical parts.

Rockshaft l5 parallel to shaft 4 is free to turn in bushings l6 and H carried by shell 2. Piece 58 is attached to the shell 2 at [9. Mercury switch clip 2G is fixed to the inner end of the rockshaft l5 so as to convert rocking movement into make-and-break control of circuits to be described later. The switch EE is held by the clip fill.

Rockshait l5 carries swinging lever arm 22 rigidly affixed, and also collar or sleeve 23 carrying lug 2311, which in some constructions may be integral with the arm 22 or with the shaft iii. Sleeve 23 is sawcut longitudinally at a l to grip flexible lever blade 25 in a pinch fit. When rock shaft moves with a mechanical restraint at 55 the remote end of blade 25, the lever blade is flexed right or left as the force is applied.

Roller 26 is mounted to rotate on shaft 21 in clip 28 fixed to the outer end of blade 25. The roller 26 intersects the tooth space of star wheel 9, by reason of the spacing distance between shafts 4 and |5, the length of blade between shafts |5 and 21 and the radius of the roller 26. Roller shaft 21 projects and is notched at 29 to receive one end of toggle spring 30, the pin 3|, end of arm 22, being notched at 32 to receive the other end of said spring. Stops 33 and 34 on plate |8 limit the rocking movement of the assembly consisting of shaft I5, mercury switch 2|, blade 25, lug 23a and arm 22 which they may strike at the limiting positions.

The operation of this arrangement of my device is as follows: The mercury switch 2| is connected to the control of circuits of the fuel flow and combustion generating system of an oil, coal or other fuel burner system.

When the system is cold, the relative positions of the parts are as shown in Figure 3. On the increasing heat phase of the cycle, the element I expands, thereby rotating rod 4 as shown by the arrow in Figure 2, causing star wheel 9 to lever the roller 26 and blade 25 to the right as in that figure. Continuation of increasing heat can only ratchet the star wheel teeth past the roller 26 and blade 25. The action has caused the toggle formed by arm 22, flexible blade 25 and spring 3|) attached at 29 and 3|, to move past center, rocking the mercury switch 2| to the position of Figure 2. The unique reinforcing action of the flexible blade 25 upon the toggle motion during the shift to increasing heat has now become a means for permitting ratcheting. Stop 33' prevents further motion of arm 22 to the right, as in Figure 2.

Now, regardless of how many teeth of star Wheel 9 may ratchet past roller 26, the mechanism is pre-set to shiftv the toggle action, and the controlled mercury switch 2| in the opposite direction immediately upon the cooling of element I. The first increment of motion in cooling, applied to star wheel 9 picks up roller 26 and flexes blade 25 to the left, adding tensional stress to spring as net toggle arm distances between 29 and 3| increase.

At the instant the toggle returns past center to the left position, the force of spring 30 is added to that of element and blade 25 changes from right-hand flexure to left-hand flexure. This rocks sleeve 23, shaft l5, arm 22 and switch 2| to the position of Figure 3, stop 34 preventing further motion similarly to the action of stop 33 in Figure 2. While cooling continues, further rotation of star wheel 9 can only flex the blade 25, permitting ratcheting action. During a static interval the relative positioning of the parts is undisturbed, the functioning of the mechanism, however, being such that in every instance the device is self-pre-set for the next thermal change of phase, increasing or decreasing as the case may be.

Roller 26 may be replaced by a common pawl of any form, for decrease in manufacturing expense, or else the end of blade 25 may be formed to act as a flexible pawl, depending upon the requirements of the designer. Star Wheel 9 may have one or manyteeth, as fineness or coarseness of desired motion, or sluggish or rapid response of element 5 determines the net motion needed to rock the mercury switch 2|.

This mechanism has few moving parts, may

work under extremely small loads, and is not affected by heat in its response characteristics, except insofar as the moduli of elasticity of springs 25 and 30 may be affected. The utilization of rolling contact between the star wheel 9 as a. force applicator, and the roller 26 as a force receiver, provides a sensitive mechanism having only rolling friction to overcome, whereas static friction in such mechanisms creates undesirable variations in lag effects tending to diminish the necessarily high safety factor for such equipment.

When a deliberate amount of lag is needed, to establish a controlled number of degrees of movement of element before the change-over takes place, the loose-key construction of Figure 3a is utilized. Key I0 aflixed to shaft 4 may rock in recess 35 in star wheel 9, held by springs 36 and 31, at the limits of movement. The range of permitted relative motion of key N] in recess 35 is the measure of deliberate lag utilized, and may serve elements such as in which a overly rapid initial response is followed by a variable curve of thermal response as against one having a comparatively straight line or more uniform response, This part of the invention extends the range of materials which may be used in the thermal elements such as I, which frequently, in heat producing plants, are of expensive metals because of high temperature operating ranges to be covered. For example, single orunitary metal elements may be used instead of high differential bi-metallic elements.

The electrical circuits operable by my invention are manifold. The leads 38, 39, and 40 of my Figure 1 may be connected with a wide range of combustion control devices such as blower and fuel controls to illustrate the principles taught by my invention.

In gas fired burners, as another example, the rocking of mercury switch 2| toward cool may regulate the blower openings or air vents, or shut off the blower circuit, while the fuel supply is cut down through a second circuit, the pilot burner remaining on. Should the pilot burner blow out, the circuit may be arranged to shut off completely all blower air and fuel supply. My invention is not directed to such art, except as a means adapted to maintain safety operation over a wide range of installation types.

Modifications of the principles of my invention are shown in Figures 4 and 5, wherein a gearing and sector arm mechanism is arranged to provide selective ratio transfer of movement between actuator shaft and rockshaft.

In Figure 4, the remote end of element moves rod 4 as in Figure 1, to which is attached primary gear 4| acting as a lever meshing with idler gear 42 rotating freely on rockshaft l5. Sector lever arm 43 is toothed at 44, and fixed to rockshaft I5, moving between frame stops and 46. The teeth 44 during the mid-part of the stroke between stops 45-46 of arm 43, are positively meshed with primary gear 4|, but at the end points of the stroke ride clear. Sector arm 43 carries pin 41 notched at 48 to hold spring 53, the other end of which is fastened to insulator at 49, aligned vertically with the shafts I5 and 4.

Stops 4546 are formed of the material of the shell or frame 2, being flexible to afford yieldingstop action. If not properly spaced, the stops may be bent to position. The lower end 5|! of sector arm 43 has affixed blade spring 5|, similar to blade 25 of Figure 1, which is pawl formed at 52, so, as to intersect'constantly the teeth of idler wheel H. The direction of pressure of blade spring is radial to idler wheel 42 so that ratcheting action in either direction of rotation may be had.

Spring 53 serves as a toggle, similar to the function of spring 30 of Figure 1.

Figure 5 shows the assembly in the decreasing heat, or cold position. The angular position of blade 5| and pawl end 52 is such with respect to the clear position of sector teeth 44 of arm 43 that the first increment of motion of the warming element I causes teeth 44 to mesh with the teeth of the primary wheel 4! since sector arm 43 is restrained to travel with the idler wheel 42 by pawl 52. Continuation of motion clockwise moves pin 41 of arm 43 past center with respect to shaft l5 and the point 49, whereupon spring 53 assists in the rapid movement of arm 43 and shaft I5 carrying mercury switch 2| to the new position shown in dashed lines in Figure 5. When stop limits further movement of arm 43, the teeth of idler wheel 42 ratchet past pawl 52, and the element I may warm to its limit of temperature response without further result on the switch rocking device.

The reverse phase of the heat cycle tends in Figure 5 to rotate primary wheel l4 clockwise, idler wheel 42 counterclockwise, and rock sector arm 43 to the left into the position shown in Figure 5. Stop 46 limits the motion and the teeth of wheel 42 ratchet again in the opposite direction, until the arrival at cold temperature, or until a new reversal of the heat cycle toward warming.

One advantage of this structure is the ability to adapt different sizes of gears such as 4!! and 42 to the desired response characteristics. For a given thermal element I of sluggish metal, or operating on a low heat range, the travel of shaft IS with respect to shaft 4 may be made fast by using a large gear for the primary gear M and a smaller gear for the idler wheel 42, and an opposite arrangement when slow travel is required. The arrangement of Figures 4 and 5 then provides a flexibility of operation which only requires a replacement of different sized gears to shift the response characteristics to accommodate a new set of operating conditions to be encountered by the device. This constitutes means to vary the fulcrum and net lever arms between thermal actuator and the switch control mechanism. While it is common practise in gearing to substitute gear pairs for varying relative speed effects between shafts, it is believed novel to provide variable fulcrum means in control mechanisms of this character.

A second modification of my invention is shown in Figures 6 and 7, wherein difierential lock and release mechanism is used to transfer effort from the thermal unit I to the rockshaft 05. This arrangements provides extremely rapid action in that the utilization of differential means may double the angular movement of the driven shaft I5 with respect to the primary shaft 4.

Shaft 4 has affixed differential carrier 54 and planet spindles 55 on which planets 56 rotate, the latter meshing with sun gears 57 and 58.

The arrangement is concentric, so that rockshaft l5 and gear 58 may be rotatably supported on an extension of shaft 4, the mechanism providing a compact construction placeable in a small space. Sun gear 58 is aiiixed to rockshaft l5 and sun gear 51 rotates freely on shaft 4 as a bearing support. Flexible blade 59 secured to the frame 2 at 60 carries ball 6| intersecting the peripheral teeth 52 of sun gear 51.

Sungear58ahowninFigure8hasaflnger l3 projecting to intersect stops t4 and 65 afiixed to the frame 2. The spring 56 shown in Figure 9 is for the purpose of delaying the return action of switch 2|, shaft l5 and gear 58 to initial cold position upon heat reduction transmitted to the element l of Figure 6.

The operation of this modification is quite similar to that described preceding, although differences will be noted. When thermal action causes element i to unwind, mercury switch 2! is initially in the position of Figure 8. Rod 4 rotates differential carrier 54 counterclockwise as in Figure 8, and planet wheels 55 fulcruming on sun gear 51 held by spring blade 59 and ball 6| apply an increased angular movement to sun gear 58 and to the rockshaft l5 and switch 2i. When the finger 63 strikes stop 65, the mercury switch 2| will then occupy the position of the dashed lines of Figure 8, while continued force application from element l and rod 4 through carrier 54 will be dissipated through ratcheting between teeth 62 of gear 51 and ball 6i held by blade 59. Any reversal of heat phase will cause a doubly increased movement of gear 58, shaft l5 and switch 2i in the opposite direction, thereby providing an extremely sensitive response where required. Spring 66 of Figure 9 is shown to illustrate means to accentuate movement toward hot position from cold, as against accelerated movement toward cold position from hot, whereby a separate response characteristic may be utilized on the increasing heat phase, compared with the decreasing phase. The spring may be arranged to speed up the decreasing phase while retarding the increasing phase without departing from my invention. It is preferred, however, in certain oil burner controls, to decelerate slightly the cut-ofi safety action, which is the reason for the specific showing of Figure 9.

Figure 10 shows the detail of construction of the blade 59 and ball ti acting as a ratchet on gear 5'17 of Figure 7.

The application of my invention to coal, oil, gas or other fuel systems requires specific structures beyond the scope of my invention, such as dampers, variable air and fuel flow controls, traveler feed, air and fuel blast, thermostats, time switches, motor control switches, ignition devices and switches and the like,

Such accessory items are well known, and do not constitute subject matter in and of my invention. The sequence of events in a general device of such character is that when cold and the starting switch is closed, the controls for burner and fuel discharge are energised. If after a given time no heat is generated such as to energise the thermal element l of the so-called stack switch, the controls self-deenergise, and the starting switch may be reset, to begin all over again.

However, if heat is generated the thermal element l is energised, and the mercury switch establishes the normal running conditions of fuel feed and blower control. However, should the burner, for instance, prime water, extinguishing the blaze head, the mercury switch 2i will be rocked to cut-off or cold'position immediately, by the thermal element l and intervening mechanism, restoring the initial fuel feed and blower control settings for starting conditions.

This much is given so as to clearly identify my invention with an example in the associated arts. The mechanisms herein shown and described are primarily for safety controls for oil, coal and gas burner systems for generating steam or other heating apparatus,

for dwellings. boats or power gt plants, and with small modifications, directly adaptable to other heat generating means. Changes in the construction and arrangement of the parts may also be made without departing from the spirit of the invention or its fundamental disclosures.

I claim:

1. The combination of a tilting mercury switch movable between stops, a rockable holder for said switch, a heat-responsive movable element, interposed diiferential mechanism between said holder and said element eifective to transmit positive motion therebetween upon initial movement of said element under either increasing or decreasing heat variation, and conjoint means operative to permit relative motion therebetween after a given degree of initial movement.

2. In controls for heat generating systems, in combination, a combustion space; a cyclically operating thermal element energised by combustion changes in said space, continuously movable switch actuating mechanism connected to said element, positive engaging means embodied in said mechanism and including a differential device, and additional means to inhibit the action of said first named means during selected portions of the cyclic operation of said element.

3. Switch actuating means comprising a first lever, a second lever, a third lever connected to a switch, a common pivot for said second and third levers, interengaging means between said first and second levers whereby movement of one may cause corresponding movement of the other, limiting members effective to define the range of motion of said third lever, biasing means operative to stress said third lever into limited positions between said members, and means adapted to permit continuing relative motion in one direction between said first and second levers when said third lever is acted upon by said biasingmeans.

4. In combustion control devices, in combination, a thermally responsive element translating heat into motion in increasing and decreasing rotational directions, combustion control mechanism connected to and moved rotationally by said element, and a control device embodying differential means effective to translate motion of said element at increasing angular ratio to said mechanism upon initial movement of said element in either direction.

5. In combustion system devices, in combination, a thermally movable element operative in increasing and decreasing heat directions, combustion controls actuated by said element, mechanism effective to move said controls at one rate upon thermal activity of said element in an increasing direction, and means operative to move said controls at a difierent rate upon thermal ac tivity of said element in a decreasing direction.

6. The combination of a heat-responsive element movable cyclically in alternate increasing and decreasing heat phases, an electrical switch,

and differentially acting mechanism moved by said element active upon said switch embodying means initially engaged and thereafter frictionally released until the next reversal of heat phase of said element.

7. The combination of a thermal unit movable under increasing and decreasing applied temperature, an electric switch, means operative to effect movement of said switch upon a given rate of motion developed by said element under increasing heat, and additional means operative to provide a diiferent rate under decreasing heat applied to said element.

8. In combination, a switching means to be acted upon, and a mechanical cyclic motion rotating device having two end-point positions and an intermediate shifting interval, embodying a resilient mechanism including a rotating force transmitting member operating positively during said interval, while idling rotationally after the completion of said interval, whereby initial rotating movement causes operation of said means followed by idling rotational motion incapable of further operation of said means by virtue of the resilience of said mechanism.

9. In combustion control devices in combination, a thermal element, an electrical switch, and an intermediate mechanism embodying a diiTerential gear device effective to rock said switch to either of two positions at increasing rates in either direction of motion upon actuation by said element.

10. The combination of an electrical switch, a thermal element, a rod actuated thereby, a primary wheel fixed to said rod, an idler wheel meshed therewith, asectored member engageable with said primary wheel between free positions and connected to said switch, means effective upon initial thermal reversal of said element to engage said member and thereby move said switch, and engagement release means effective upon completion of said motion to free said member.

11. In a control for combustion systems in combination, a heat responsive device, an oscillatable shaft having a flexible radial arm mounted to oscillate thereon and operable by said heat responsive device, a switch to be operated by said shaft, an operating lever secured to said shaft and a tension spring connecting the ends of said resilient arm and said operating lever for effecting a snap action of said switch.

12. In combination, a rotary heat responsive device, a wheel member actuable by said heat responsive device, an oscillatory switch carrier, a switch fixedly mounted on said switch carrier, a flexible arm having yieldable engagement with said wheel member, and mechanism controlled by said flexible arm for causing immediate motion of said switch carrier on change of direction of rotation of said heat responsive device.

DANIEL C. WILKERSON. 

